I recently moved back home after my house fire xmas day 2019 and have been finishing the basement. There is alot of drywall dust and saw dust that has been getting sucked up into the basement return filter. It is its own zone.

I have a 18x18 filter that i have banged out and vacumed 2 or 3 times not wanting to replace it knowing im going to clog it in a day or two.

Tonight I got to thinking, is there another filter in the attic with unit that might be getting whatever dust makes it passed the return filter? The contractor didn't mention it.

I dont want to call a service tech if its something I can maintain myself.

Usually no. If there’s one inside there is rarely one at the unit. Knowing most homeowners won’t climb up there every three months.

One filter for each return zone.

Multiple filter grills and filters, but stacking filters is rare in residential systems.
They are out there, but are very rare.

BTW, residential systems are not supposed to be in operation during remodeling and contruction work.
Damage (stress) on the equipment can happen real quick with the lack of proper airflow.

FWIW, I just changed my furnace filter. Though the woodstove is the usual source of heat, filters are relatively cheap.

The filter looked O.K., it’s been 6 months or so. When I’m not around, the gas furnace kicks in occasionally.